Bass leaves after amp warms up?


I don't understand-after my Musical Fidelity M6i amp warms up for about an hour I notice the deep bass & kick drum aren't the same.
They sound less musical with loss of weight/depth.The notes are there but the moving of air have left.Sound is has much less impact and boreing.
I had the same problem with Bryston amp so there is no defect with amps nor with the rest of my equipment/
PSB Synchrony one speakers,AQ cables,Bryston CD Player.
My question has anyone heard similar & is there a plausable reason?
fishing716
For me it reminded me of the the need to make sure fundamentals (like proper wiring) are correct and not assume that just because someone does not like what they hear, that it is necessarily the equipment's fault. I knew all of that already I suppose but this was a good reminder to sometimes expect the unexpected.
Another lesson learned for me was when something is not going right, keep things as simple as possible. For example, don't attempt to bi-wire right out of the gate. Audiophiles (including myself) tend to make things more complicated over time.

WHen something goes wrong, you have to isolate the problem. That's harder to do as the system configuration becomes more complex. The best approach may be to stip things back down to a minimum, and regression test from there. That may still often require having spare pieces around to swap in and out for comparison when needed.